996AD,
While you will notice the handling improvement inmedioately, you need to wait till they settle to achieve the final ride height. They will be higher in the begginning for a few hundred miles. So take a photo now and one later to compare.
Also, there is a +/-10mm variance from each set, so if you happen to get a suspension set that is +10mm higher than average, you won't notice much drop, and if you get one from the other extreme, -10mm than the average RoWM030 the you will get a really low stance like a GT3's. I'am in my second set on RoWM030 and both were within the average specs. After they settle, why don't you post a photo of the wheel/wheel arch and you can compare to mine (I'll post a pic of mine) to see how low it is.
The swaybars are thinker/stiffer than the stock ones, but the US M030 swaybars are the same as the RoWM030 one (the shocks and springs aren't)
You can use the Eibach springs with the RoWM030 shocks because these shocks are stiffer than stock and can handle and match better the stiffer Eibach springs, but you will affect handling somewhat though because they weren't designed to exactly match each other and achieve a balanced and specific handling objective, though it won't be nearly as bad an using the stock shocks. So some people use the M030 shocks in order to be able to lower the car with stiffer aftermarket lowering springs. However if your objective was lowering the car significantly you had the two the options instead of the RoWM030 as I explained above, like the PSS9's which are height adjustable to your liking.
Here is a great article on the specific effects of the US M030 and RowM030 and what they were designed for:
http://www.pca.org/panorama/sample_article_3.html
and an underground carparc which does not allow me to lower the car to much. In other words more cosmetic. I will give them a call monday and see if they can arrange the fitting 
